Out of Darts
At $50/month, it did show me where I have economic nexus. After several months of $50 charges, I find out that they are delaying Auto-file as an option, but offer no concession in the meantime. I feel that the app isn't worth it just for the data, as I was sold on the auto-file option (at additional cost).
This data isn't helpful without auto-file, so do your homework before signing up. You'll still need to file manually to take care of your sales tax due. This is potentially hundreds of data entries per state.